Merge branch 'sn/osxkeychain-rust-universal'

The build system has been updated to support building universal macOS
binaries when 'Rust' is enabled, by compiling separate static archives
for each target triple listed in 'RUST_TARGETS' and combining them
using the macOS 'lipo' tool.  The 'git-credential-osxkeychain' helper
has been updated to link against '$(RUST_LIB)' when 'Rust' is enabled.

* sn/osxkeychain-rust-universal:
  contrib: wire up osxkeychain in contrib/Makefile on macOS
  Makefile: support universal macOS builds via RUST_TARGETS
  Makefile: add $(RUST_LIB) prerequisite to osxkeychain

Makefile

@@ -500,6 +500,14 @@ include shared.mak
 #
 # Building Rust code requires Cargo.
 #
+# Define RUST_TARGETS if you want to cross-compile. If left unspecified, it uses
+# the default Rust target on the system.
+#
+# On macOS, this supports specifying multiple targets, separated by a space.
+# This will produce a Universal static library using `lipo`.
+#
+# Example: RUST_TARGETS="aarch64-apple-darwin x86_64-apple-darwin"
+#
 # == SHA-1 and SHA-256 defines ==
 #
 # === SHA-1 backend ===
@@ -939,16 +947,19 @@ TEST_SHELL_PATH = $(SHELL_PATH)
 
 LIB_FILE = libgit.a
 
+ifndef NO_RUST
 ifdef DEBUG
-RUST_TARGET_DIR = target/debug
+RUST_BUILD_CONFIG = debug
 else
-RUST_TARGET_DIR = target/release
+RUST_BUILD_CONFIG = release
 endif
 
 ifeq ($(uname_S),Windows)
-RUST_LIB = $(RUST_TARGET_DIR)/gitcore.lib
+RUST_LIB_NAME = gitcore.lib
 else
-RUST_LIB = $(RUST_TARGET_DIR)/libgitcore.a
+RUST_LIB_NAME = libgitcore.a
+endif
+RUST_LIB = target/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME)
 endif
 
 GITLIBS = common-main.o $(LIB_FILE)
@@ -3020,11 +3031,35 @@ scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 
+ifndef NO_RUST
+ifeq ($(RUST_TARGETS),)
 $(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(LIB_FILE)
 	$(QUIET_CARGO)cargo build $(CARGO_ARGS)
+else
+ifneq ($(words $(RUST_TARGETS)),1)
+ifneq ($(uname_S),Darwin)
+$(error Building universal Rust libraries requires macOS (lipo is not available on $(uname_S)))
+endif
+endif
+
+RUST_MEMBER_LIBS = $(foreach target,$(RUST_TARGETS),target/$(target)/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME))
+$(RUST_MEMBER_LIBS): target/%/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME): Cargo.toml $(RUST_SOURCES) $(LIB_FILE)
+	$(QUIET_CARGO)cargo build $(CARGO_ARGS) --target $*
+
+$(RUST_LIB): $(RUST_MEMBER_LIBS)
+	$(call mkdir_p_parent_template)
+	$(QUIET_GEN)\
+	if test $(words $(RUST_TARGETS)) -gt 1; \
+	then \
+		lipo -create $^ -output $@; \
+	else \
+		cp $< $@; \
+	fi
+endif
 
 .PHONY: rust
 rust: $(RUST_LIB)
+endif
 
 export DEFAULT_EDITOR DEFAULT_PAGER
 
@@ -4075,7 +4110,8 @@ $(LIBGIT_HIDDEN_EXPORT): $(LIBGIT_PARTIAL_EXPORT)
 contrib/libgit-sys/libgitpub.a: $(LIBGIT_HIDDEN_EXPORT)
 	$(AR) $(ARFLAGS) $@ $^
 
-contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) GIT-LDFLAGS
+# When Rust is enabled, git-credential-osxkeychain depends on Rust symbols in $(RUST_LIB)
+contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) $(RUST_LIB) GIT-LDFLAGS
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
 		$(filter %.o,$^) $(LIBS) -framework Security -framework CoreFoundation
 

contrib/Makefile

@@ -1,10 +1,22 @@
+include ../config.mak.uname
+-include ../config.mak.autogen
+-include ../config.mak
+
+
+ifeq ($(uname_S),Darwin)
+OS_CONTRIB += credential/osxkeychain
+endif
+
 all::
+	$(foreach dir,$(OS_CONTRIB),$(MAKE) -C $(dir) $@;)
 
 test::
 	$(MAKE) -C diff-highlight $@
 	$(MAKE) -C subtree $@
+	$(foreach dir,$(OS_CONTRIB),$(MAKE) -C $(dir) $@;)
 
 clean::
 	$(MAKE) -C contacts $@
 	$(MAKE) -C diff-highlight $@
 	$(MAKE) -C subtree $@
+	$(foreach dir,$(OS_CONTRIB),$(MAKE) -C $(dir) $@;)

contrib/credential/osxkeychain/Makefile

@@ -10,4 +10,6 @@ install:
 clean:
 	$(MAKE) -C ../../.. clean-git-credential-osxkeychain
 
-.PHONY: all git-credential-osxkeychain install clean
+test: git-credential-osxkeychain
+
+.PHONY: all git-credential-osxkeychain install clean test